1. Field of the Invention
The present invention relates to fluid systems and, more particularly, to an improved system for increasing pressure in piped fluid systems, and related methods.
2. Background of the Related Art
In piped fluid systems, pumps or similar machines are sometimes used to elevate the pressure of the fluid, in order to overcome supply pressure deficiencies or pipe losses, to satisfy equipment pressure requirements (particularly in modern, low-emission or high-efficiency equipment), or for any other desired reason. Commonly called “boosters,” such systems and related methods perform mechanical work on fluid received at the inlet, thereby increasing the pressure of the fluid discharged at the outlet.
Booster systems and methods may be used to increase the pressure of piped gases such as natural gas, propane or propane-air mixtures, air, digester gas, landfill gas, and others. Gas boosters are commonly installed upstream of commercial or industrial natural gas-fired or propane-fired equipment, such as rooftop heating, ventilation and air conditioning (HVAC) units, boilers, process heat systems, heat-treating furnaces, incinerators, gas-fired coolers, standby generators or other machinery, which may be employed in a variety of applications. For example, U.S. Pat. No. 6,484,490 B1 to Olson et al. describes the use of a pump to provide a gaseous fuel to a combustion chamber which produces an exhaust. Gas boosters may be utilized in urban areas, particularly in such areas with older supply networks which operate at low supply pressures, or in high consumption areas (such as those with heavy extensive industrial applications) which can experience “drooping” or reduced supply pressures during periods of increased demand. Also, gas boosters may be applied to systems in remote regions which may not have sufficient pressure due to pipe losses or leaks, or for other reasons.
Gas boosters can comprise a rotating machine, sometimes called a “fan blower,” comprising a housing, a fluid suction inlet, a fluid discharge outlet, a motor, a shaft, and at least one impeller or rotor, commonly called a “fan wheel.” Fluid enters the housing through the inlet, and the motor rotates a shaft connected to the fan wheel, creating rotational kinetic energy. Fluid then comes into contact with a rotating fan wheel, and the rotational kinetic energy is converted to stored potential energy in the fluid, in the form of pressure. Typically, such motors may be either constant-speed or variable speed motors of any type. Furthermore, gas boosters may be operated alone or in connection with other pressure-elevating systems, and configured in series or in parallel, such as in duplex-type systems, to satisfy the necessary flow and pressure requirements of the fluid system, or to provide redundancy. Gas booster systems may also include isolation valves for isolating the fan blower or pump for maintenance or repairs, or in emergency situations; check valves, for preventing undesired directional flow; a bypass, for allowing flow through the fluid system when the gas booster is not operating or when the booster is isolated; any associated connections to the pump and/or motor, or any monitoring equipment. For the purposes of the present disclosure, those of skill in the art will recognize that the terms impeller, rotor and fan wheel may be used interchangeably, to refer to a rotating apparatus which comes into contact with and performs work on the piped fluid, thereby increasing its pressure. Similarly, those of skill in the art will also recognize that the terms fan blower and pump may be used interchangeably.
Typically, the flow capacity and pressure gain of a gas booster are functions of the booster's design characteristics. When the motor is energized, and the desired fan wheel speed is reached, the booster differential pressure (defined as the pressure difference between the inlet and the outlet) remains constant. Thus, as the fluid supply pressure to the booster fluctuates, the discharge pressure will also fluctuate by a corresponding amount, for a given constant fan wheel speed. The constant booster differential pressure is sometimes referred to as the “pressure gain” of the booster system. The maximum volumetric flow capacity of the gas booster is generally a function of the axial width of fan wheel rotating within the booster, while the maximum pressure gain is typically a function of the radial length of the fan wheel blade, which acts as a lever arm in performing work on the piped fluid. Theoretically, gas boosters may be designed to increase the pressure of fluid flowing at any flow rate, and to achieve any desired pressure gain.
Despite the aforementioned advantages associated with the use of gas boosters, there are a number of physical and operational limitations which hinder the widespread use of prior art systems and methods in piped fluid systems in general, and in natural gas or propane applications in particular. For example, in some gas boosters of the prior art, motors are typically located outside of the fluid flow path, and a shaft extends from the motor into the fan wheel housing to rotate the fan wheel and perform work on the fluid. In such systems, a fan or other heat sink must be provided to cool the electronic components of the motor, which generate heat during normal operation, and seals must be provided around the rotating shaft to prevent pressure losses in the housing, due to shaft leakage. While some gas boosters feature motors that are positioned within the path of the flowing fluid, thereby removing heat from the motor by convective heat transfer, such boosters may not be readily adapted for use with multiple sources of power, and must be manually reconfigured or adjusted to accommodate electric power at different voltage levels or frequencies. Moreover, in gas boosters of the prior art, the alignment of the discharge outlet piping is typically limited to one or a small number of standard positions, and may not be readily adjusted in the field to accommodate varying system configurations or operating conditions. This limitation tends to reduce the functionality of a typical gas booster, and also complicates its physical installation into piped fluid systems.
In view of the foregoing, a need exists for improved gas booster systems and methods for use in piped gas systems in general, and in natural gas or propane systems in particular. It is an object of the present invention to overcome one or more drawbacks and/or disadvantages of related systems and methods of the prior art.